1. Field of the Invention
The present invention relates to a position measuring arrangement for measuring the relative position of a first object with respect to a second object, and also to a method for assembling a position measuring arrangement for measuring the relative position of a first object with respect to a second object.
2. Discussion of Related Art
Position measuring arrangements in the form of angle and linear measuring arrangements are widely employed in the machine tool industry and in other production, handling and testing systems. For reasons of space, so-called modular measuring arrangements are often employed, whose graduation support and scanning devices are delivered as separate elements, and the exact assignment of these two elements relative to each other takes place only when they are installed in the objects to be measured. Angle measuring arrangements constructed in this manner are also called built-in angle encoders, which do not have their own bearing.
In the course of position measuring, the graduation of the graduation support is scanned in a contactless manner by a scanning element of the scanning device, and position-dependent scanning signals are obtained. The size and quality of the scanning signals depends on the scanning distance, for which reason it is necessary to mount the graduation support during installation at an optimal distance from the scanning element of the scanning device.
Such a position measuring arrangement is known from EP 0 353 395 B1 in the form of an angle-measuring arrangement, as well as such a method for assembling the angle-measuring arrangement. To make installation on the objects to be measured easier, the position assignment between the graduation support and the scanning device which is required for operations, has already been fixed by the manufacturer of the angle-measuring arrangement by the provision of grooves. These grooves are used for the mutual alignment of the graduation support and the scanning device by means of an alignment element.
In U.S. Pat. No. 4,794,250, the entire contents of which are incorporated herein by reference, the alignment element is a housing part, which can be rotated around the axis of the angle-measuring arrangement which, for setting the scanning distance, is inserted between a limit stop of the scanning device active in the direction of the scanning distance and a limit stop of the graduation support active in the direction of the scanning distance. After setting and installing the components of graduation support and scanning device on the objects to be measured, the alignment element is removed from the limit stop of the graduation support by rotating it.
In this case it is disadvantageous that the position of the limit stops must be preset by highly accurate processing. Therefore very close tolerances must be observed, which makes manufacturing expensive.
To solve this problem it had already been proposed in EP 0 973 014 B1 to produce the positive connection required for providing the scanning distance by crowding the scanning device or the graduation support. It is disadvantageous here, that the material must be specially designed for this.